tests: suppress output on switcheroo tests

The output from the switcheroo tests is voluminous and
(because it includes timestamps) highly sensitive to
minor changes, leading to extremely large updates to the
reference outputs.  This patch addresses this problem
by suppressing output from the tests.  An internal
parameter can be set to enable the output.  Wiring that
up to a command-line flag (perhaps even the rudimantary
-v/-q options in m5/main.py) is left for future work.

src/python/m5/simulate.py

@@ -218,7 +218,7 @@ def _changeMemoryMode(system, mode):
     else:
         print "System already in target mode. Memory mode unchanged."
 
-def switchCpus(system, cpuList, do_drain=True):
+def switchCpus(system, cpuList, do_drain=True, verbose=True):
     """Switch CPUs in a system.
 
     By default, this method drains and resumes the system. This
@@ -238,7 +238,10 @@ def switchCpus(system, cpuList, do_drain=True):
     Keyword Arguments:
       do_drain -- Perform a drain/resume of the system when switching.
     """
-    print "switching cpus"
+
+    if verbose:
+        print "switching cpus"
+
     if not isinstance(cpuList, list):
         raise RuntimeError, "Must pass a list to this function"
     for item in cpuList:

tests/configs/switcheroo.py

@@ -70,7 +70,7 @@ class Sequential:
     def first(self):
         return self.cpus[self.first_cpu]
 
-def run_test(root, switcher=None, freq=1000):
+def run_test(root, switcher=None, freq=1000, verbose=False):
     """Test runner for CPU switcheroo tests.
 
     The switcheroo test runner is used to switch CPUs in a system that
@@ -91,6 +91,7 @@ def run_test(root, switcher=None, freq=1000):
       switcher -- CPU switcher implementation. See Sequential for
                   an example implementation.
       period -- Switching frequency in Hz.
+      verbose -- Enable output at each switch (suppressed by default).
     """
 
     if switcher == None:
@@ -100,6 +101,11 @@ def run_test(root, switcher=None, freq=1000):
     system = root.system
     system.mem_mode = type(current_cpu).memory_mode()
 
+    # Suppress "Entering event queue" messages since we get tons of them.
+    # Worse yet, they include the timestamp, which makes them highly
+    # variable and unsuitable for comparing as test outputs.
+    m5.internal.core.cvar.want_info = verbose
+
     # instantiate configuration
     m5.instantiate()
 
@@ -113,12 +119,13 @@ def run_test(root, switcher=None, freq=1000):
         if exit_cause == "simulate() limit reached":
             next_cpu = switcher.next()
 
-            print "Switching CPUs..."
-            print "Next CPU: %s" % type(next_cpu)
+            if verbose:
+                print "Switching CPUs..."
+                print "Next CPU: %s" % type(next_cpu)
             m5.drain(system)
             if current_cpu != next_cpu:
                 m5.switchCpus(system, [ (current_cpu, next_cpu) ],
-                              do_drain=False)
+                              do_drain=False, verbose=verbose)
             else:
                 print "Source CPU and destination CPU are the same, skipping..."
             m5.resume(system)